This Swimline pool cover fits 21 x 33-foot above-ground oval pools and is great for keeping your pool in good condition during the cold, winter months, but it will also make getting your pool back into shape in the spring much easier by keeping debris out of your pool.This pool cover is made of laminated polyethylene sheeting woven with thick, high density polyethylene stitching, which ensures superior tensile strength and durability. It has also been treated to provide maximum resistance to damaging ultraviolet rays. Attach it with the included grommets, steel cable and winch. Its dimensions are 21 x 41 feet to provide sufficient overlap when covering a 21 x 33-foot oval pool.For the long life of your pool, choose this Swimline pool cover.